In a conventional semiconductor light emitting device employing InGaAlP based compound semiconductor, for example, a semiconductor layered portion 10, in which a light emitting layer forming portion 3 having a double hetero-junction structure made of InGaAlP based semiconductor material, a window layer 4 made of AlGaAs based semiconductor material, and a contact layer 5 are laminated, is deposited on a semiconductor substrate made of GaAs. And a first electrode 6 made of an Au—Be alloy, or the like, is provided on the contact layer 5, and a second electrode 7 made of an Au—Ge alloy, or the like, is provided on the rear face of the semiconductor substrate, as shown in FIG. 3.
There is a problem that most of the light emitted and advanced toward the substrate is absorbed and lost in the above structure, because GaAs of the substrate is a material that absorbs light emitted in the light emitting layer forming portion 3. Therefore, a light emitting device having the following structure has been proposed to increase an efficiency of deriving light emitted, as shown in for example, Japanese Unexamined Patent Publication 2001-339100, and attached FIG. 4. That is, the GaAs substrate is removed after the semiconductor layered portion 10, having the above described structure, is deposited on the GaAs substrate, and then a silicon substrate 1, or the like, is adhered to the semiconductor layered portion 10 via a metal layer 2 formed of an Au—Ge alloy layer 2a, a layer 2b made of Au, Al, or Ag, and an Au layer 2c, so that a light is reflected from an inserted metal layer 2.
The metal layer 2 is inserted on the substrate side of the light emitting layer forming portion as described above, and thereby, the light emitted in the light emitting layer forming portion and advanced toward the substrate, is reflected by the metal layer 2 so as to be emitted from the top surface effectively. This structure is considered to be useful.
As a result of research by the present inventors concerning the efficiency of deriving light in the above described structure shown in FIG. 4, however, it has been found that the increase in the efficiency of deriving light is slight in actuality, taking into consideration the time and effort needed to replace the substrate. Therefore, a further increase in the brightness is desired from the point of view of the cost efficiency.